Is the Komodo dragon the only dragon in the world?

Well, it is technically not a Dragon, the name just says 'Dragon' in it because the Komodo Dragon is one of the larger reptiles on Earth.

The Komodo dragon is the largest monitor lizard species, but is smaller than crocodiles and alligators, and many large snakes such as pythons and anacondas.

Komodo "Dragons" are not really dragons at all. They're just hyperbolically-named lizards.